We plan to study the structure, conformation, absolute configuration and changes in conformation of a series of siderophores and their iron chelates in order to obtain a better understanding about the active transport of these molecules in microbial organisms. New siderophores and those with antibiotic activity will also be investigated. In addition, non-planar peptide bonds and cycloretroenantiomerism and a cyclic peptide antibiotic-nucleotide complex will be investigated. The methods employed will be primarily single crystal X-ray diffraction, but also CD and Mossbauer spectroscopy. The undersigned agrees to accept responsibility for the scientific and technical conduct of the research project and for provision of required progress reports if a grant is awarded as the result of this application.